使用私有变量的Javascript构建器模式 [英] Javascript builder pattern using private variables

问题描述

我试图在Javascript中创建一个使用私有变量的构建器模式，同时提供一个公共访问器（ fullName ），该访问器返回所有其他属性的混搭。 这个问题和答案表明我可以在人员构造函数中使用 Object.defineProperty 来访问私有变量，但这不起作用- instance.fullName 始终为未定义。

I'm trying to create a builder pattern in Javascript that uses private variables, while providing one public accessor (fullName) that returns a mashup of all the other properties. This question and answer suggests that I can use Object.defineProperty inside the person constructor in order to access private variables, but it doesn't work - instance.fullName is always undefined.

我该如何工作，以使构建器模式变量保持私有，但是公共访问者可以在整个构建链中访问它们吗？

How can I get this working so that the builder pattern variables remain private, but the public accessor has access to them throughout the build chain?

var Person = function () {
    var _firstName, _lastName

    Object.defineProperty(this, "fullName", {
        get: function () {
            return _firstName + ' ' + _lastName;
        }
    });

    return {
        firstName: function (n) {
            _firstName = n
            return this
        },
        lastName: function (n) {
            _lastName = n
            return this
        }
    }
}

var x = new Person().firstName('bob').lastName('dole');

console.log(x.fullName); // always undefined

推荐答案

根据我的评论，传递给 defineProperty（）的对象：

As per my comment, change the object passed to defineProperty():

var Person = function () {
    var _firstName, _lastName

    var _self = {
        firstName: function (n) {
            _firstName = n
            return this
        },
        lastName: function (n) {
            _lastName = n
            return this
        }
    }

    Object.defineProperty(_self, "fullName", {
        get: function () {
            return _firstName + ' ' + _lastName;
        }
    });

    return _self;
}

var x = new Person().firstName('bob').lastName('dole');

console.log(x.fullName); // bob dole

http://jsfiddle.net/mattball/peztf9qs/

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